Optical deflector

ABSTRACT

An optical deflector includes a magnet unit, which generates a magnetic field, and a movable plate unit, which is placed in the magnetic field. The movable plate unit has an inner movable plate having a reflecting surface, an outer movable plate, two inner torsion bars connecting the inner and outer movable plates, a support located outside the outer movable plate, and two outer torsion bars connecting the outer movable plate and support. The movable plate unit has two inner drive wiring portions that extend along by a periphery of the inner movable plate. The magnet unit includes magnets, two adjacent magnets of which are opposite in magnetic polarity direction. The inner drive wiring portions extend almost parallel to boundaries between the two adjacent magnets and are respectively located substantially immediately above the boundaries. Currents of the same direction are applied to the two inner drive wiring portions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Applications No. 2003-405787, filed Dec. 4, 2003;and No. 2004-328815, filed Nov. 12, 2004, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electromagnetically actuated opticaldeflector.

2. Description of the Related Art

Recently, attention has been paid to an optical deflector manufacturedby using a micromachining technique based on a semiconductormanufacturing technique.

The specification of U.S. Pat. No. 6,388,789 discloses, as such anoptical deflector, an electromagnetically actuated two-dimensionaloptical deflector. FIG. 13 is a perspective view of the main part of theoptical deflector disclosed in U.S. Pat. No. 6,388,789. FIG. 14 is asectional perspective view of the optical deflector disclosed in U.S.Pat. No. 6,388,789.

As shown in FIG. 13, this two-dimensional optical deflector includes afirst rotating portion 1002, which can rock about the first rotationaxis with respect to a support 1001, and a second rotating portion 1003,which can rotate rock the second rotation axis with respect to the firstrotating portion 1002. The second rotating portion 1003 has a reflectingsurface for reflecting light. The support 1001 and first rotatingportion 1002 are coupled to each other through a pair of hinges 1004 and1004B extending along the first rotation axis. The first rotatingportion 1002 and second rotating portion 1003 are coupled to each otherthrough a pair of hinges 1005 and 1005B extending along the secondrotation axis.

A pair of first coils 1061 and 1062 for enabling rocking about the firstrotation axis and a pair of second coils 1071 and 1072 for enablingrocking about the second rotation axis are formed on the second rotatingportion 1003. The first coils 1061 and 1062 are connected to each otherthrough a wiring 1006. The second coils 1071 and 1072 are connected toeach other through a wiring 1007. Two wirings 1006A for supplying powerto the first coils 1061 and 1062 extend on the pair of hinges 1004 and1004B, respectively, via the first rotating portion 1002. Likewise, twowirings 1007A for supplying power to the second coils 1071 and 1072extend on the pair of hinges 1004 and 1004B, respectively, via the firstrotating portion 1002.

As shown in FIG. 14, a magnet 1100 is placed below the second rotatingportion 1003. The magnet 1100 generates a magnetic field 1089 radiallyspreading from the center of the second rotating portion 1003 to thesupport 1001. The second rotating portion 1003 is rocked about the firstrotation axis by the interaction between the currents flowing in thefirst coils 1061 and 1062 and the magnetic field 1089, and also aboutthe second rotation axis by the interaction between the currents flowingin the second coils 1071 and 1072 and the magnetic field 1089.

U.S. Pat. No. 6,404,313 discloses another electromagnetically actuatedtwo-dimensional optical deflector. FIG. 15 is an exploded perspectiveview of the optical deflector disclosed in U.S. Pat. No. 6,404,313.

As shown in FIG. 15, this two-dimensional optical deflector includes anouter movable plate 2002 located inside a support 2001, an inner movableplate 2003 located inside the outer movable plate 2002, a first torsionbar 2004 supporting the support 2001 so as to allow it to rock about theX-axis with respect to the outer movable plate 2002, and a secondtorsion bar 2005 supporting the inner movable plate 2003 so as to allowit to rock about the Y-axis with respect to the outer movable plate2002. The inner movable plate 2003 has a reflecting surface 2104 forreflecting light.

A first driving coil 2102 with a single turn extends on the outermovable plate 2002. A second driving coil 2103 with a single turnextends near a peripheral portion on the inner movable plate 2003. Thefirst driving coil 2102 is connected to the second driving coil 2103.

A pair of magnets 2105 and 2106 are arranged along a diagonal lineoutside this structure. The magnetic field generated by the magnets 2105and 2106 exists on one of the diagonal lines. The inner movable plate2003 is rocked about the X-axis by the interaction between the currentflowing in the first driving coil 2102 and the magnetic field, and torock about the Y-axis by the interaction between the current flowing inthe second driving coil 2103 and the magnetic field.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to an electromagnetically actuatedtwo-dimensional optical deflector, which can deflect a light beam abouttwo axes. The optical deflector according to the present inventioncomprises a magnet unit, which generates a magnetic field, and a movableplate unit, which is placed in the magnetic field. The movable plateunit has an inner movable plate having a reflecting surface, an outermovable plate located outside the inner movable plate, two inner torsionbars connecting the inner movable plate and the outer movable plate, asupport located outside the outer movable plate, and two outer torsionbars connecting the outer movable plate and the support. The innertorsion bars extend along a first axis and are capable of twisting aboutthe first axis so as to allow the inner movable plate to tilt about thefirst axis with respect to the outer movable plate. The outer torsionbars extend along a second axis perpendicular to the first axis and arecapable of twisting about the second axis so as to allow the outermovable plate to tilt about the second axis with respect to the support.The movable plate unit further has two inner drive wiring portions thatextend along by a periphery of the inner movable plate. The magnet unitincludes magnets, two adjacent magnets of which are opposite in magneticpolarity direction. The inner drive wiring portions extend substantiallyparallel to boundaries between the two adjacent magnets and arerespectively located substantially immediately above the boundaries.Currents of the same direction are applied to the two inner drive wiringportions.

The present invention is directed to an electromagnetically actuatedone-dimensional optical deflector, which can deflect a light beam onlyabout one axis. The optical deflector according to the present inventioncomprises a magnet unit, which generates a magnetic field, and a movableplate unit, which is placed in the magnetic field. The movable plateunit has a movable plate having a reflecting surface, a support locatedoutside the movable plate, and two torsion bars connecting the movableplate and the support. The torsion bars extend along one axis and arecapable of twisting about the axis so as to allow the movable plate totilt about the axis with respect to the support. The movable plate unitfurther has two drive wiring portions that extend along by a peripheryof the movable plate. The magnet unit includes magnets, two adjacentmagnets of which are opposite in magnetic polarity direction. The drivewiring portions extend substantially parallel to boundaries between thetwo adjacent magnets and are respectively located substantiallyimmediately above the boundaries. Currents of the same direction areapplied to the two inner drive wiring portions.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Advantages of the invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the present invention.

FIG. 1 is a sectional perspective view of an optical deflector accordingto the first embodiment of the present invention;

FIG. 2 is a perspective view of the movable plate unit shown in FIG. 1;

FIG. 3 is a plan view of the movable plate unit shown in FIG. 2;

FIG. 4 is a plan view of the magnet unit shown in FIG. 1;

FIG. 5 is a sectional perspective view of an optical deflector accordingto the second embodiment of the present invention;

FIG. 6 is a plan view of the magnet unit shown in FIG. 5;

FIG. 7 is a sectional perspective view of an optical deflector accordingto the third embodiment of the present invention;

FIG. 8 is a plan view of the movable plate unit shown in FIG. 7;

FIG. 9 is a plan view of the magnet unit shown in FIG. 7;

FIG. 10 is a sectional perspective view of an optical deflectoraccording to the fourth embodiment of the present invention;

FIG. 11 is a plan view of the movable plate unit shown in FIG. 10;

FIG. 12 is a plan view of the magnet unit shown in FIG. 10;

FIG. 13 is a perspective view of the main part of the optical deflectordisclosed in U.S. Pat. No. 6,388,789;

FIG. 14 is a sectional perspective view of the optical deflectordisclosed in U.S. Pat. No. 6,388,789; and

FIG. 15 is an exploded perspective view of the optical deflectordisclosed in U.S. Pat. No. 6,404,313.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the present invention will be described below withreference to the views of the accompanying drawing.

FIRST EMBODIMENT

FIG. 1 is a sectional perspective view of an optical deflector accordingto the first embodiment of the present invention. FIG. 2 is aperspective view of a movable plate unit shown in FIG. 1. The movableplate unit shown in FIG. 2 is an upside down view of that shown inFIG. 1. FIG. 3 is a plan view of the movable plate unit shown in FIG. 2.FIG. 4 is a plan view of a magnet unit shown in FIG. 1.

As shown in FIG. 1, a two-dimensional optical deflector 100 includes amagnet unit 170, which generates a magnetic field, and a movable plateunit 110 placed in the magnetic field generated by the magnet unit 170.The movable plate unit 110 and magnet unit 170 are arranged at apredetermined interval.

As shown in FIGS. 2 and 3, the movable plate unit 110 includes an innermovable plate 112 in the form of a rectangular plate, an outer movableplate 116 in the form of a rectangular frame located outside the innermovable plate 112, two inner torsion bars (first inner torsion bar 114 aand second inner torsion bar 114 b) connecting the inner movable plate112 and the outer movable plate 116, a support 120 in the form of arectangular plate located outside the outer movable plate 116, and twoouter torsion bars (first outer torsion bar 118 a and second outertorsion bar 118 b) connecting the outer movable plate 116 and thesupport 120.

Although the outer movable plate 116 is in the form of a framesurrounding the inner movable plate 112, the form of the outer movableplate 116 is not specifically limited to this. Although the support 120is in the form of a frame surrounding the outer movable plate 116, theform of the support 120 is not limited to this, and may have anothershape such as a U shape. In addition, the support 120 is formed from onemember, but may be formed from two members that are spaced apart fromeach other.

As shown in FIG. 1, the inner movable plate 112 has, on its uppersurface, a reflecting surface 122 for reflecting light. The reflectingsurface 122 is formed from, for example, a thin gold (Au) film. In thiscase, the upper surface of the inner movable plate 112 is one of the twolargest parallel flat surfaces. Referring to FIG. 1, the upper surfaceis the one seen and located on the upper side. In addition, referring toFIG. 1, the surface that is located on the lower side and is hidden fromthe eye will be referred to as a lower surface.

As shown in FIGS. 2 and 3, the two inner torsion bars 114 a and 114 bextend on an almost straight line along a first axis A1. The two outertorsion bars 118 a and 118 b also extend on an almost straight linealong a second axis A2. The first and second axes A1 and A2 are almostperpendicular to each other.

The outer peripheral shape of the inner movable plate 112 is rectangularwhen viewed from above, and two central axes of the rectangle (two axeswhich pass through the center of the rectangle and are perpendicular tosides of the rectangle), which are perpendicular to each other, areparallel to the first axis A1 and second axis A2, respectively. Theouter peripheral shape of the outer movable plate 116 is rectangularwhen viewed from above, and two central axes of the rectangle (two axeswhich pass through the center of the rectangle and are perpendicular tosides of the rectangle), which are perpendicular to each other, are alsoparallel to the first axis A1 and second axis A2.

The outer torsion bars 118 a and 118 b are capable of twisting about thesecond axis A2 and allow the outer movable plate 116 to tilt about thesecond axis A2 with respect to the support 120. The inner torsion bars114 a and 114 b are capable of twisting about the second axis and allowthe inner movable plate 112 to rock about the first axis A1 with respectto the outer movable plate 116.

Consequently, the direction of the reflecting surface 122 of the innermovable plate 112 is allowed to be two-dimensionally changed, so thatthe two-dimensional optical deflector 100 allows a beam of lightreflected by the reflecting surface 122 to be deflected.

The movable plate unit 110 is formed from a silicon substrate by using akind of semiconductor fabrication process. The inner movable plate 112and outer movable plate 116 are formed from, for example, thin siliconplates obtained by processing a silicon substrate. The inner torsionbars 114 a and 114 b and outer torsion bars 118 a and 118 b are formedfrom, for example, a thin silicon film or thin polyimide film. Thematerial to be used for the inner movable plate 112, outer movable plate116, support 120, inner torsion bars 114 a and 114 b, and outer torsionbars 118 a and 118 b may include poly silicon, silicon nitride, anorganic material, a metal material, and the like in addition to siliconand polyimide.

As shown in FIG. 3, the movable plate unit 110 further includes twoinner wirings (first inner wiring 130 a and second inner wiring 130 b)extending on the inner movable plate 112, inner torsion bars 114 a and114 b, outer movable plate 116, outer torsion bars 118 a and 118 b, andsupport 120. The first inner wiring 130 a includes a first inner drivewiring portion 132 a and two first inner extracted wiring portions 134 aand 136 a respectively extending from the two ends of the first innerdrive wiring portion 132 a. Likewise, the second inner wiring 130 bincludes a second inner drive wiring portion 132 b and two second innerextracted wiring portions 134 b and 136 b respectively extending fromthe two ends of the second inner drive wiring portion 132 b.

In this case, the inner drive wiring portions 132 a and 132 b are partsof the inner wirings 130 a and 130 b that actually contribute to theactuation of the inner movable plate 112 and extend parallel to thefirst axis A1 along by a periphery of the inner movable plate 112. Thefirst inner extracted wiring portions 134 a and 136 a are parts of thefirst inner wiring 130 a that exclude the first inner drive wiringportion 132 a. Likewise, the second inner extracted wiring portions 134b and 136 b are parts of the second inner wiring 130 b that exclude thesecond inner drive wiring portion 132 b.

As is obvious from FIG. 3, the first inner drive wiring portion 132 aand second inner drive wiring portion 132 b are located almostline-symmetrically with respect to the first axis A1.

Referring to FIG. 3, the first inner extracted wiring portion 134 aextending from the left end portion of the first inner drive wiringportion 132 a on the upper side extends downward along by the peripheryof the inner movable plate 112, passes through the first inner torsionbar 114 a on the left side, extends upward along by the inner peripheryof the outer movable plate 116, passes through the first outer torsionbar 118 a on the upper side, extends to the left on the support 120, andterminates at an electrode pad 144 a provided on the support 120.

The first inner extracted wiring portion 136 a extending from the rightend portion of the first inner drive wiring portion 132 a extendsdownward along by the periphery of the inner movable plate 112, passesthrough the second inner torsion bar 114 b on the right side, extendsupward along by the periphery of the outer movable plate 116, passesthrough the first outer torsion bar 118 a on the upper side, extends tothe right on the support 120, and terminates at an electrode pad 146 aprovided on the support 120.

As is obvious from FIG. 3, the first inner extracted wiring portion 134a and first inner extracted wiring portion 136 a are located almostline-symmetrically with respect to the first axis A1.

The second inner extracted wiring portion 134 b extending from the leftend portion of the second inner drive wiring portion 132 b on the lowerside extends upward along by the periphery of the inner movable plate112, passes through the first inner torsion bar 114 a on the left side,extends downward along by the periphery of the outer movable plate 116,passes through the second outer torsion bar 118 b on the lower side,extends to the left on the support 120, and terminates at an electrodepad 144 b provided on the support 120.

The second inner extracted wiring portion 136 b extending from the rightend portion of the second inner drive wiring portion 132 b extendsupward along by the periphery of the inner movable plate 112, passesthrough a second inner torsion bar 114 b on the right side, extendsdownward along by the inner periphery of the outer movable plate 116,passes through the second outer torsion bar 118 b on the lower side,extends to the right on the support 120, and terminates at an electrodepad 146 b provided on the support 120.

As is obvious from FIG. 3, the second inner extracted wiring portion 134b and second inner extracted wiring portion 136 b are located almostline-symmetrically with respect to the second axis A2.

The movable plate unit 110 further includes two outer wirings (firstouter wiring 150 a and second outer wiring 150 b) extending on the outermovable plate 116, outer torsion bars 118 a and 118 b, and support 120.The first outer wiring 150 a includes a first outer drive wiring portion152 a and two first outer extracted wiring portions 154 a and 156 arespectively extending from the two ends of the first outer drive wiringportion 152 a. Likewise, the second outer wiring 150 b includes a secondouter drive wiring portion 152 b and two second outer extracted wiringportions 154 b and 156 b respectively extending from the two ends of thesecond outer drive wiring portion 152 b.

In this case, the outer drive wiring portions 152 a and 152 b arerespectively parts of the outer wirings 150 a and 150 b that actuallycontribute to the actuation of the outer movable plate 116 and extendparallel to the second axis A2 along by a periphery of the outer movableplate 116. The first outer extracted wiring portions 154 a and 156 a areparts of the first outer wiring 150 a that exclude the first outer drivewiring portion 152 a. Likewise, the second outer extracted wiringportions 154 b and 156 b are parts of the second outer wiring 150 b thatexclude the second outer drive wiring portion 152 b.

As is obvious from FIG. 3, the first outer drive wiring portion 152 aand second outer drive wiring portion 152 b are located almostline-symmetrically with respect to the second axis A2.

Referring to FIG. 3, the first outer extracted wiring portion 154 aextending from the upper end portion of the first outer drive wiringportion 152 a on the left side extends to the right along by the outerperiphery of the outer movable plate 116, passes through the first outertorsion bar 118 a on the upper side, extends to the left on the support120, and terminates at an electrode pad 164 a provided on the support120.

The first outer extracted wiring portion 156 a extending from the lowerend portion of the first outer drive wiring portion 152 a extends to theright along by the outer periphery of the outer movable plate 116,passes through the second outer torsion bar 118 b on the lower side,extends to the left on the support 120, and terminates at an electrodepad 166 a provided on the support 120.

As is obvious from FIG. 3, the first outer extracted wiring portion 154a and first outer extracted wiring portion 156 a are located almostline-symmetrically with respect to the first axis A1.

The second outer extracted wiring portion 154 b extending from the upperend portion of the second outer drive wiring portion 152 b on the rightside extends to the left along by the outer periphery of the outermovable plate 116, passes through the first outer torsion bar 118 a onthe upper side, extends to the right on the support 120, and terminatesat an electrode pad 164 b provided on the support 120.

The second outer extracted wiring portion 156 b extending from the lowerend portion of the second outer drive wiring portion 152 b extends tothe left along by the outer periphery of the outer movable plate 116,passes through the second outer torsion bar 118 b on the lower side,extends to the right on the support 120, and terminates at an electrodepad 166 b provided on the support 120.

As is obvious from FIG. 3, the second outer extracted wiring portion 154b and second outer extracted wiring portion 156 b are located almostline-symmetrically with respect to the first axis A1.

Although not specifically shown, the wirings 130 a, 130 b, 150 a, and150 b are preferably covered with isolation film such as silicon oxidefilm for electric isolation.

The wirings 130 a, 130 b, 150 a, and 150 b and the electrode pads 144 a,144 b, 146 a, 146 b, 164 a, 164 b, 166 a, and 166 b are formed fromaluminum by using, for example, a semiconductor fabrication process.

For example, the wirings 130 a, 130 b, 150 a, and 150 b and theelectrode pads 144 a, 144 b, 146 a, 146 b, 164 a, 164 b, 166 a, and 166b are formed by forming an aluminum film on the surface of a structureincluding the inner movable plate 112, outer movable plate 116, support120, inner torsion bars 114 a and 114 b, and outer torsion bars 118 aand 118 b formed from a silicon substrate using a kind of semiconductorfabrication process as described above, and by patterning the film.

The material to be used for the wirings 130 a, 130 b, 150 a, and 150 band the electrode pads 144 a, 144 b, 146 a, 146 b, 164 a, 164 b, 166 a,and 166 b may be copper or gold (Au) instead of aluminum, preferably ametal having a low resistivity.

As shown in FIG. 4, a magnet unit 170 includes a magnet 172 located atthe center, two magnets 174 a and 174 b located on the two sides of themagnet 172 along the first axis A1, and two magnets 176 a and 176 blocated on the two sides of the magnet 172 along the second axis A2. Themagnet 172 has an N pole on the side facing the movable plate unit 110.The magnets 174 a and 174 b and the magnets 176 a and 176 b each have anS pole on the side facing the movable plate unit 110. That is, the twoadjacent magnets are opposite in magnetic polarity direction. Themagnets, 172, 174 a, 174 b, 176 a, and 176 b each have a rectangularparallelepiped shape, and are fixed to each other with an adhesive.

As shown in FIG. 1, the movable plate unit 110 and magnet unit 170 arearranged at a predetermined interval. The inner drive wiring portions132 a and 132 b extend almost parallel to the boundaries between themagnet 172 and the magnets 174 a and 174 b. Although the second innerdrive wiring portion 132 b is not shown in FIG. 1, the positionalrelationship with the second inner drive wiring portion 132 b can easilybe understood by referring to FIGS. 3 and 4. The outer drive wiringportions 152 a and 152 b extend almost parallel to the boundariesbetween the magnet 172 and the magnets 176 a and 176 b.

The first inner drive wiring portion 132 a is located almost immediatelyabove the boundary between the magnet 172 and the magnet 174 a. Thesecond inner drive wiring portion 132 b is located almost immediatelyabove the boundary between the magnet 172 and the magnet 174 b. Thefirst outer drive wiring portion 152 a is located almost immediatelyabove the boundary between the magnet 172 and the magnet 176 a. Thesecond outer drive wiring portion 152 b is located almost immediatelyabove the boundary between the magnet 172 and the magnet 176 b. In thiscase, “immediately above” indicates a direction that is perpendicular toboth the first and second axes A1 and A2 and extends from the magnetunit 170 to the movable plate unit 110.

In this arrangement relationship, the magnetic flux density near theboundary between two adjacent magnets with opposite magnetic polaritydirections is high. That is, the first inner drive wiring portion 132 ais located in a region where the magnetic flux density is high. Thesecond inner drive wiring portion 132 b is located in a region where themagnetic flux density is high. Likewise, the first outer drive wiringportion 152 a is located in a region where the magnetic flux density ishigh. The second outer drive wiring portion 152 b is located in a regionwhere the magnetic flux density is high.

As shown in FIG. 1, magnetic lines of force flowing from the magnet 172to the magnet 174 a are almost perpendicular to the boundary between themagnet 172 and the magnet 174 a, and hence cross the first inner drivewiring portion 132 a at almost right angles. Likewise, magnetic lines offorce flowing from the magnet 172 to the magnet 174 b are almostperpendicular to the boundary between the magnet 172 and the magnet 174b, and hence cross the second inner drive wiring portion 132 b at almostright angles. Magnetic lines of force flowing from the magnet 172 to themagnet 176 a are almost perpendicular to the boundary between the magnet172 and the magnet 176 a, and hence cross the first outer drive wiringportion 152 a at almost right angles. Likewise, magnetic lines of forceflowing from the magnet 172 to the magnet 176 b are almost perpendicularto the boundary between the magnet 172 and the magnet 176 b, and hencecross the second outer drive wiring portion 152 b at almost rightangles.

The operation of the above optical deflector will be described next.

For example, a drive power supply (not shown) is used to apply a voltagebetween the electrode pad 164 a and the electrode pad 166 a to cause acurrent to flow from the electrode pad 164 a to the electrode pad 166 a.In addition, the same voltage is applied between the electrode pad 164 band the electrode pad 166 b to cause the same current to flow from theelectrode pad 164 b to the electrode pad 166 b.

Referring to FIG. 3, a downward current flows in the first outer drivewiring portion 152 a on the outer movable plate 116. The first outerdrive wiring portion 152 a is located in outward (leftward) magneticlines of force, and hence receives the downward Lorentz force in adirection perpendicular to the drawing surface.

Referring to FIG. 3, a downward current flows in the second outer drivewiring portion 152 b on the outer movable plate 116. The second outerdrive wiring portion 152 b is located in outward (rightward) magneticlines of force, and hence receives the upward Lorentz force in thedirection perpendicular to the drawing surface.

The outer movable plate 116 therefore receives a couple of forces aboutthe second axis A2, and the outer torsion bars 118 a and 118 b twist.This causes the outer movable plate 116 to tilt about the second axisA2. As a consequence, the inner movable plate 112 tilts about the secondaxis A2 together with the outer movable plate 116. The tilt angle of theouter movable plate 116 depends on the magnitudes of the currentsflowing in the outer drive wiring portions 152 a and 152 b.

For example, a drive power supply (not shown) is used to apply a voltagebetween the electrode pad 144 a and the electrode pad 146 a to cause acurrent to flow from the electrode pad 144 a to the electrode pad 146 a.In addition, a voltage is applied between the electrode pad 144 b andthe electrode pad 146 b to cause a current to flow from the electrodepad 144 b to the electrode pad 146 b.

Referring to FIG. 3, a rightward current flows in the first inner drivewiring portion 132 a on the inner movable plate 112. The first innerdrive wiring portion 132 a is located in outward (upward) magnetic linesof force, and hence receives the upward Lorentz force in the directionperpendicular to the drawing surface.

Referring to FIG. 3, a rightward current flows in the second inner drivewiring portion 132 b on the inner movable plate 112. The second innerdrive wiring portion 132 b is located in outward (downward) magneticlines of force, and hence receives the downward Lorentz force in thedirection perpendicular to the drawing surface.

The inner movable plate 112 therefore receives a couple of forces aboutthe first axis A1, and the inner torsion bars 114 a and 114 b twist.This causes the inner movable plate 112 to tilt about the first axis A1.The tilt angle of the inner movable plate 112 depends on the magnitudesof the currents flowing in the inner drive wiring portions 132 a and 132b.

When the inner movable plate 112 is actuated, the Lorentz force as aforce component that causes the outer movable plate 116 to tilt aboutthe second axis A2 is generated in each of parts of the first innerextracted wiring portions 134 a and 136 a that are located on the outermovable plate 116. However, the Lorentz forces received by the firstinner extracted wiring portions 134 a and 136 a cancel out each other,so that the forces do not contribute to the tilting of the outer movableplate 116.

More specifically, part of the first inner extracted wiring portion 134a that is located on the outer movable plate 116 and extends parallel tothe second axis A2 receives the downward Lorentz force in the directionperpendicular to the drawing surface. In addition, part of the firstinner extracted wiring portion 136 a that is located on the outermovable plate 116 and extends parallel to the second axis A2 receivesthe downward Lorentz force in the direction perpendicular to the drawingsurface. Since the magnitude of the current flowing in the first innerextracted wiring portion 134 a is equal to that of the current flowingin the first inner extracted wiring portion 136 a, the magnitude of theLorentz force received by the first inner extracted wiring portion 134 ais equal to the magnitude of the Lorentz force received by the firstinner extracted wiring portion 136 a.

The Lorentz force received by the first inner extracted wiring portion134 a and the Lorentz force received by the first inner extracted wiringportion 136 a are both components that causes the outer movable plate116 to tilt about the second axis A2. However, the two components makethe outer movable plate 116 tilt in opposite directions. For thisreason, the Lorentz force received by the first inner extracted wiringportion 134 a and that received by the first inner extracted wiringportion 136 a cancel out each other, and hence make substantially nocontribution to the tilting of the outer movable plate 116 about thesecond axis A2.

This equally applies to the second inner extracted wiring portions 134 band 136 b.

This makes it possible to independently control the tilting of the innermovable plate 112 about the first axis A1 and that about the second axisA2.

More preferably, the magnitude of the current flowing in the first innerwiring 130 a is equal to the magnitude of the current flowing in thesecond inner wiring 130 b. In this case, currents flow in oppositedirections in two parts of the first inner extracted wiring portion 134a and second inner extracted wiring portion 134 b that are located onthe outer movable plate 116 and extend almost parallel to the secondaxis A2 (located relatively near each other on the left side on theouter movable plate 116). For this reason, the Lorentz forces generatedin the respective portions by the interaction with magnetic fieldscancel out each other. This also applies to the first inner extractedwiring portion 136 a and second inner extracted wiring portion 136 b.For this reason, the currents that flow in the inner wirings 130 a and130 b for tilting the inner movable plate 112 have no influence on thetilting of the outer movable plate 116. This makes it possible toindependently control the tilting of the inner movable plate 112 aboutthe first axis A1 and that about the second axis A2.

The two-dimensional optical deflector 100 of this embodiment cantherefore realize almost completely independent control on the tiltingof the inner movable plate 112 about the first axis A1 and that aboutthe second axis A2.

When, for example, the two-dimensional optical deflector 100 is to beused to scan a light beam, AC voltages are applied between the electrodepads 164 a and 166 a and between the electrode pads 164 b and 166 b tomake in-phase AC currents flow in the outer wirings 150 a and 150 b. Inthis case, since the magnitudes of the currents flowing in the firstouter drive wiring portions 152 a and 152 b periodically change, thetilt angle of the outer movable plate 116 about the second axis A2repeatedly changes. That is, the outer movable plate 116 is rocked aboutthe second axis A2. In addition, AC voltages are applied between theelectrode pads 144 a and 146 a and between the electrode pads 144 b and146 b to make AC currents flow in the inner wirings 130 a and 130 b. Inthis case, since the magnitudes of the currents flowing in the innerdrive wiring portions 132 a and 132 b periodically change, the tiltangle of the inner movable plate 112 about the first axis A1 repeatedlychanges. That is, the inner movable plate 112 is rocked about the firstaxis A1. As a consequence, the light beam reflected by the reflectingsurface 122 of the inner movable plate 112 is two-dimensionally scanned.

When the two-dimensional optical deflector 100 is to be used to deflecta light beam in a predetermined direction, constant voltages are appliedbetween the electrode pads 164 a and 166 b and between the electrodepads 164 b and 166 b to make DC currents flow in the same direction inthe outer wirings 150 a and 150 b. In this case, since the magnitudes ofthe currents flowing in the outer drive wiring portions 152 a and 152 bare constant, the outer movable plate 116 tilts about the second axis A2by a predetermined angle. That is, the outer movable plate 116 isdeflected about the second axis A2. In addition, DC voltages are appliedbetween the electrode pads 144 a and 146 a and between the electrodepads 144 b and 146 b to make DC currents flow in the inner wirings 130 aand 130 b. In this case, since the magnitudes of the currents flowing inthe inner drive wiring portions 132 a and 132 b are constant, the innermovable plate 112 tilts about the first axis A1 by a predeterminedangle. That is, the inner movable plate 112 is deflected about the firstaxis A1. As a consequence, the light beam reflected by the reflectingsurface 122 of the inner movable plate 112 is deflected in apredetermined direction.

As is obvious from the above description, the two-dimensional opticaldeflector 100 of this embodiment can make almost completely independentcontrol on the rocking and deflection of the inner movable plate 112having the reflecting surface about the first axis A1 and second axisA2. In addition, since the drive wiring portions 132 a, 132 b, 152 a,and 152 b are arranged in the regions where the magnetic flux densitiesare high, and the magnetic lines of forces generated by the magnet unit170 cross the drive wiring portions 132 a, 132 b, 152 a, and 152 b atright angles regardless of their positions, the actuation efficiency ishigh, and the power consumption is low.

According to the above description, currents of the same magnitude aremade to flow in the two inner wirings 130 a and 130 b. However, it isnot always necessary to make currents of the same magnitude flow inthese wirings. The magnitudes of currents to be made to flow in the twoinner wirings 130 a and 130 b may differ within the range in which theoperation characteristics required for the two-dimensional opticaldeflector 100 are satisfied. In order to realize independent controlsuitable for rocking about the first axis A1 and second axis A2, themagnitudes of currents to be made to flow in the two inner wirings 130 aand 130 b are preferably equal to each other.

Although two wirings are provided for each of the inner movable plate112, outer movable plate 116, and movable plate 212 in this embodiment,one wiring may be provided for each of them. That is, one wiringincluding two drive wiring portions may be provided for each of theinner movable plate 112, outer movable plate 116, and movable plate 212.

SECOND EMBODIMENT

This embodiment is directed to another two-dimensional opticaldeflector. FIG. 5 is a sectional perspective view of the opticaldeflector according to the second embodiment of the present invention.FIG. 6 is a plan view of a magnet unit in FIG. 5.

The optical deflector of this embodiment differs from that of the firstembodiment only in the arrangement of the magnet unit.

As shown in FIG. 5, a two-dimensional optical deflector 100A of thisembodiment includes a movable plate unit 110 and magnet unit 180. Themovable plate unit 110 is identical to that in the first embodiment. Asshown in FIGS. 5 and 6, the magnet unit 180 includes a magnet 182located at the center and a magnet 184 surrounding the magnet 182. Themagnet 182 has an N pole on the side facing the movable plate unit 110.The magnet 184 has an S pole on the side facing the movable plate unit110. That is, the magnets 182 and 184 are opposite in magnetic polaritydirection. The magnet 182 has a rectangular parallelepiped shape. Themagnet 184 has a through hole in which the magnet 182 is fitted. Themagnet 182 is placed in this through hole. Therefore, the outerperipheral shape of the magnet 182 is rectangular when viewed fromabove.

As shown in FIG. 5, the movable plate unit 110 and magnet unit 180 arearranged at a predetermined interval. Each of inner drive wiringportions 132 a and 132 b extends almost parallel to the boundary betweenthe magnets 182 and 184 along a first axis. Although the second innerdrive wiring portion 132 b is not shown in FIG. 5, the positionalrelationship with it can be easily understood by referring to FIGS. 3and 6. Outer drive wiring portions 152 a and 152 b extend almostparallel to the boundaries between the magnets 182 and 184 along asecond axis A2.

In addition, the inner drive wiring portions 132 a and 132 b are locatedalmost immediately above the boundary between the magnets 182 and 184along the first axis A1. The outer drive wiring portions 152 a and 152 bare located almost immediately above the boundary between the magnets182 and 184 along the second axis A2.

In this arrangement relationship, as in the first embodiment, all thedrive wiring portions 132 a, 132 b, 152 a, and 152 b are located in theregions where the magnetic flux densities are high. In addition, themagnetic lines of force passing through the inner drive wiring portions132 a and 132 b cross them at almost right angles, and the magneticlines of force passing through the outer drive wiring portions 152 a and152 b cross them at almost right angles.

In the two-dimensional optical deflector 100A of this embodiment, amagnetic circuit is positioned in accordance with the position of thehole in the magnet 184. This facilitates positioning the magnet 182.Therefore, in addition to the advantages of the first embodiment,positioning of the magnet is facilitated, and the process is simplified.

THIRD EMBODIMENT

This embodiment is directed to an optical deflector, whichone-dimensionally deflects a light beam. FIG. 7 is a sectionalperspective view of the optical deflector according to the thirdembodiment of the present invention. FIG. 8 is a plan view of themovable plate unit shown in FIG. 7. FIG. 9 is a plan view of the magnetunit shown in FIG. 7.

As shown in FIG. 7, an optical deflector 200 includes a magnet unit 270,which generates a magnetic field, and a movable plate unit 210, which isplaced in the magnetic field generated by the magnet unit 270. Themovable plate unit 210 and magnet unit 270 are arranged at apredetermined interval.

As shown in FIG. 8, the movable plate unit 210 includes a movable plate212, a support 220 located outside the movable plate 212, and twotorsion bars (first torsion bar 218 a and second torsion bar 218 b)connecting the movable plate 212 and the support 220.

The support 220 is in the form of a frame surrounding the movable plate212. However, the form of the support 220 is not limited to this, andmay have another form such as U-shaped form. In addition, the support220 comprises one member, but may comprise two members spaced apart fromeach other.

As shown in FIG. 7, the movable plate 212 has, on its upper surface, areflecting surface 222 for reflecting light. The reflecting surface 222comprises, for example, a thin gold (Au) film.

As shown in FIG. 8, the two torsion bars 218 a and 218 b extend on analmost straight line along an axis A. The outer peripheral shape of themovable plate 212 is rectangular when viewed from above, and the centralaxis of the rectangle (the axis that passes through the center of therectangle and is perpendicular to its side) is parallel to the axis A.The torsion bars 218 a and 218 b are capable of twisting about the axisA so as to allow the movable plate 212 to tilt about the axis A withrespect to the support 220.

This makes it possible to one-dimensionally change the direction of thereflecting surface 222 of the movable plate 212. The optical deflectorarray 200 can therefore one-dimensionally deflect the light beamreflected by the reflecting surface 222.

The movable plate unit 210 is formed from a silicon substrate by using akind of semiconductor fabrication process. The movable plate 212 isformed from, for example, a thin silicon plate obtained by processing asilicon substrate. The torsion bars 218 a and 218 b are formed from, forexample, a thin silicon film or thin polyimide film. The material to beused for the movable plate 212, support 220, and torsion bars 218 a and218 b may include poly silicon, silicon nitride, an organic material, ametal material, and the like in addition to silicon and polyimide.

As shown in FIG. 8, the movable plate unit 210 further includes twowirings (first wiring 250 a and second wiring 250 b) extending on themovable plate 212, torsion bars 218 a and 218 b, and support 220. Thefirst wiring 250 a includes a first drive wiring portion 252 a and twofirst extracted wiring portions 254 a and 256 a extending from the twoends of the first drive wiring portion 252 a, respectively. Likewise,the second wiring 250 b includes a second drive wiring portion 252 b andtwo second extracted wiring portions 254 b and 256 b extending from thetwo ends of the second drive wiring portion 252 b, respectively.

In this case, the drive wiring portions 252 a and 252 b are parts of thewirings 250 a and 250 b that actually contribute to the actuation of themovable plate 212 and extend parallel to the axis A along by theperiphery of the movable plate 212. The first extracted wiring portions254 a and 256 a are parts of the first wiring 250 a that exclude thefirst drive wiring portion 252 a. Likewise, the second extracted wiringportions 254 b and 256 b are parts of the second wiring 250 b thatexclude the second drive wiring portion 252 b.

As is obvious from FIG. 8, the first drive wiring portion 252 a andsecond drive wiring portion 252 b are located almost line-symmetricallywith respect to the axis A.

Referring to FIG. 8, the first extracted wiring portion 254 a extendingfrom the upper end portion of the first drive wiring portion 252 a onthe left side extends to the right along the outer periphery of themovable plate 212, passes through the first torsion bar 218 a on theupper side, extends to the left on the support 220, and terminates at anelectrode pad 264 a provided on the support 220.

The first extracted wiring portion 256 a extending from the lower endportion of the first drive wiring portion 252 a, extends to the rightalong by the outer periphery of the movable plate 212, passes throughthe second torsion bar 218 b on the lower side, extends to the left onthe support 220, and terminates at an electrode pad 266 a provided onthe support 220.

The second extracted wiring portion 254 b extending from the upper endportion of the second drive wiring portion 252 b on the right sideextends to the left along by the outer periphery of the movable plate212, passes through the first torsion bar 218 a on the upper side,extends to the right on the support 220, and terminates at an electrodepad 264 b provided on the support 220.

The second extracted wiring portion 256 b extending from the lower endportion of the second drive wiring portion 252 b extends to the leftalong by the outer periphery of the movable plate 212, passes throughthe second torsion bar 218 b on the lower side, extends to the right onthe support 220, and terminates at an electrode pad 266 b provided onthe support 220.

Although not specifically shown, the wirings 250 a and 250 b arepreferably covered with isolation film such as silicon oxide film forelectric isolation. Materials and forming methods suitable for thewirings 250 a and 250 b and electrode pads 264 a, 264 b, 266 a, and 266b are the same as those in the first embodiment As shown in FIG. 9, themagnet unit 270 includes a magnet 272 located at the center and twomagnets 276 a and 276 b arranged on the two sides of the magnet 272along a direction perpendicular to the axis A. The magnet 272 has an Npole on the side facing the movable plate unit 210. Each of the magnets276 a and 276 b has an S pole on the side facing the movable plate unit210. That is, the magnets 272 and 276 a are opposite in magneticpolarity direction, and the magnets 272 and 276 b are also opposite inmagnetic polarity direction. Each of the magnets 272, 276 a, and 276 bhas a rectangular parallelepiped shape, and are fixed to each other withan adhesive.

As shown in FIG. 7, the movable plate unit 210 and magnet unit 270 arearranged at a predetermined interval. The drive wiring portions 252 aand 252 b extend almost parallel to the boundaries between the magnets272, 276 a, and 276 b.

The first drive wiring portion 252 a is placed almost immediately abovethe boundary between the magnets 272 and 276 a. The second drive wiringportion 252 b is located almost immediately above the boundary betweenthe magnets 272 and 276 b. In this arrangement relationship, as shown inFIG. 7, the magnetic lines of force flowing from the magnet 272 to themagnet 276 a are almost perpendicular to the boundary between the magnet272 and the magnet 276 a, and hence cross the first drive wiring portion252 a at almost right angles. Likewise, the magnetic lines of forceflowing from the magnet 272 to the magnet 276 b are almost perpendicularto the boundary between the magnet 272 and the magnet 276 b, and hencecross the second drive wiring portion 252 b at almost right angles.

The movable plate in the optical deflector according to this embodimentis actuated in the same manner as the outer movable plate in thetwo-dimensional optical deflector according to the first embodiment.

When, for example, the optical deflector 200 is to be used to scan alight beam, AC voltages are applied between the electrode pads 264 a and266 a and between the electrode pads 264 b and 266 b to make in-phase ACcurrents flow in the wirings 250 a and 250 b. In this case, since themagnitudes of the currents flowing in the drive wiring portions 252 aand 252 b periodically change, the tilt angle of the movable plate 212about the axis A repeatedly changes. That is, the movable plate 212 isrocked about the axis A. As a consequence, the light beam reflected bythe reflecting surface 222 of the movable plate 212 is one-dimensionallyscanned.

When the optical deflector 200 is to be used to deflect a light in apredetermined direction, constant voltages are applied between theelectrode pads 264 a and 266 a and between the electrode pads 264 b and266 b to make DC currents flow in the same direction in the wirings 250a and 250 b. In this case, since the magnitudes of the currents flowingin the drive wiring portions 252 a and 252 b are constant, the movableplate 212 tilts about the axis A by a predetermined angle. That is, themovable plate 212 is deflected about the axis A. That is, the movableplate 212 is deflected about the axis A. As a consequence, the lightbeam reflected by the reflecting surface 222 of the movable plate 212 isdeflected in a predetermined direction.

As is obvious from the above description, in the optical deflector 200of this embodiment, since the drive wiring portions 252 a and 252 b arearranged in the regions where the magnetic flux densities are high, andthe magnetic lines of forces generated by the magnet unit 170 cross thedrive wiring portions 252 a and 252 b at almost right angles regardlessof their positions, the actuation efficiency is high, and the powerconsumption is low.

According to this embodiment, the magnet unit 270 comprises the threemagnets 272, 276 a, and 276 b arranged along a direction perpendicularto the axis A. However, as in the second embodiment, the magnet unit 270may comprise one magnet and another magnet surrounding it.

FOURTH EMBODIMENT

This embodiment is directed to another two-dimensional opticaldeflector. FIG. 10 is a sectional perspective view of an opticaldeflector according to the fourth embodiment. FIG. 11 is a plan view ofthe movable plate unit shown in FIG. 10. FIG. 12 is a plane view of themagnet unit shown in FIG. 10.

As shown in FIG. 10, a two-dimensional optical deflector 300 of thisembodiment includes a movable plate units 310 and magnet unit 380. Themovable plate units 310 and magnet unit 380 are arranged at apredetermined interval, and the movable plate units 310 is locatedwithin the magnetic field generated by the magnet unit 380.

As shown in FIGS. 10 and 11, the movable plate units 310 includes aninner movable plate 312 in the form of a circular plate, an outermovable plate 316 in the form of a circular frame, which is locatedoutside the inner movable plate 312, two inner torsion bars (first innertorsion bar 314 a and second inner torsion bar 314 b) connecting theinner movable plate 312 and the outer movable plate 316, a support 320in the form of a rectangular frame, which is located outside the outermovable plate 316, and two outer torsion bars (first outer torsion bar318 a and second outer torsion bar 318 b) connecting the outer movableplate 316 and the support 320.

As shown in FIG. 10, the inner movable plate 312 has, on its uppersurface, a reflecting surface 322 for reflecting light.

As shown in FIGS. 10 and 11, both the two inner torsion bars 314 a and314 b extend on an almost straight line along a first axis A1. The twoouter torsion bars 318 a and 318 b extend on an almost straight linealong a second axis A2. The first axis A1 and second axis A2 are almostperpendicular to each other.

The outer peripheral shape of the inner movable plate 312 is circularwhen viewed from above, and two central axes of the circle, which areperpendicular to each other, are parallel to the first axis A1 andsecond axis A2, respectively. The outer peripheral shape of the outermovable plate 316 is also circular when viewed from above, and twocentral axes of the circle, which are perpendicular to each other, arealso parallel to the first axis A1 and second axis A2.

The outer peripheral shape of the inner movable plate 312 may beelliptic. In this case, the two central axes (the major and minor axesof the ellipse) of the ellipse, which are perpendicular to each other,are preferably parallel to the first and second axes A1 and A2,respectively. The outer peripheral shape of the outer movable plate 316may be elliptic. In this case, the two central axes (the major and minoraxes of the ellipse) of the ellipse, which are perpendicular to eachother, are preferably parallel to the first and second axes A1 and A2,respectively.

In other words, if a circle is regarded as an ellipse in a broad sense,both the outer peripheral shape of the inner movable plate 312 and thatof the outer movable plate 316 are elliptic.

The outer torsion bars 318 a and 318 b are capable of twisting anddistorting about the second axis A2, thereby enabling the outer movableplate 316 to tilt about the second axis A2 with respect to the support320. The inner torsion bars 314 a and 314 b are capable of twisting anddistorting about the first axis A1, thereby enabling the inner movableplate 312 to tilt about the first axis A1 with respect to the outermovable plate 316.

This makes it possible to two-dimensionally change the direction of thereflecting surface 322 of the inner movable plate 312. Thetwo-dimensional optical deflector 300 can therefore two-dimensionallydeflect the light beam reflected by the reflecting surface 322.

As shown in FIG. 11, the movable plate units 310 further includes twoinner wirings (first inner wiring 330 a and second inner wiring 330 b)extending on the inner movable plate 312, inner torsion bars 314 a and314 b, outer movable plate 316, outer torsion bars 318 a and 318 b, andsupport 320. The first inner wiring 330 a includes a first inner drivewiring portion 332 a and two first inner extracted wiring portions 334 aand 336 a extending from the two ends of the first inner drive wiringportion 332 a, respectively. Likewise, the second inner wiring 330 bincludes a second inner drive wiring portion 332 b and two second innerextracted wiring portions 334 b and 336 b extending from the two ends ofthe second inner drive wiring portion 332 b.

In this case, the inner drive wiring portions 332 a and 332 b are partsof the inner wirings 330 a and 330 b that are located near peripheralportions on the inner movable plate 312 and extend along by theperiphery of the inner movable plate 312. The first inner extractedwiring portions 334 a and 336 a are parts of the first inner wiring 330a that exclude the first inner drive wiring portion 332 a. Likewise, thesecond inner extracted wiring portions 334 b and 336 b are parts of thesecond inner wiring 330 b that exclude the second inner drive wiringportion 332 b.

As is obvious from FIG. 11, the first inner drive wiring portion 332 aand second inner drive wiring portion 332 b are located almostline-symmetrically with respect to the first axis A1.

Referring to FIG. 11, the first extracted wiring portion 334 a extendingfrom the left end portion of the first inner drive wiring portion 332 aon the upper side passes through the first inner torsion bar 314 a onthe left side, extends upward along by the inner periphery of the outermovable plate 316, passes through the first outer torsion bar 318 a onthe upper side, extends to the left on a support 320, and terminates ata electrode pad 344 a provided on the support 320.

The first extracted wiring portion 336 a extending from the right endportion of the first inner drive wiring portion 332 a passes through thesecond inner torsion bar 314 b on the right side, extends upward alongby the inner periphery of the outer movable plate 316, passes throughthe first outer torsion bar 318 a on the upper side, extends to theright on the support 320, and terminates at an electrode pad 346 aprovided on the support 320.

As is obvious from FIG. 11, the first extracted wiring portion 334 a andfirst extracted wiring portion 336 a are located almostline-symmetrically with respect to the second axis A2.

The second extracted wiring portion 334 b extending from the left endportion of the second inner drive wiring portion 332 b on the lower sidepasses through the first inner torsion bar 314 a on the left side,extends downward along by the inner periphery of the outer movable plate316, passes through the second outer torsion bar 318 b on the lowerside, extends to the left on the support 320, and terminates at anelectrode pad 344 b provided on the support 320.

The second extracted wiring portion 336 b extending from the right endportion of the second inner drive wiring portion 332 b passes throughthe second inner torsion bar 314 b on the right side, extends downwardalong by the inner periphery of the outer movable plate 316, passesthrough the second outer torsion bar 318 b on the lower side, extends tothe right on the support 320, and terminates at an electrode pad 346 bprovided on the support 320.

As is obvious from FIG. 11, the second extracted wiring portion 334 band second extracted wiring portion 336 b are located almostline-symmetrically with respect to the second axis A2.

The movable plate units 310 further includes two outer wirings (firstouter wiring 350 a and second outer wiring 350 b) extending on the outermovable plate 316, outer torsion bars 318 a and 318 b, and support 320.The first outer wiring 350 a includes a first outer drive wiring portion352 a and two first outer extracted wiring portions 354 a and 356 aextending from the two ends of the first outer drive wiring portion 352a, respectively. Likewise, the second outer wiring 350 b includes asecond outer drive wiring portion 352 b and two second outer extractedwiring portions 354 b and 356 b extending from the two ends of thesecond outer drive wiring portion 352 b, respectively.

In this case, the outer drive wiring portions 352 a and 352 b are partsof the outer wirings 350 a and 350 b that extend along by the peripheryof the outer movable plate 316. The first outer extracted wiringportions 354 a and 356 a are parts of the first outer wiring 350 a thatexclude the first outer drive wiring portion 352 a. Likewise, the secondouter extracted wiring portions 354 b and 356 b are parts of the secondouter wiring 350 b that exclude the second outer drive wiring portion352 b.

As is obvious from FIG. 11, the first outer drive wiring portion 352 aand second outer drive wiring portion 352 b are located almostline-symmetrically with respect to the second axis A2.

Referring to FIG. 11, the first outer extracted wiring portion 354 aextending from the upper end portion of the first outer drive wiringportion 352 a on the left side passes through the first outer torsionbar 318 a on the upper side, extends to the left on the support 320, andterminates at an electrode pad 364 a provided on the support 320.

The first outer extracted wiring portion 356 a extending from the lowerend portion of the first outer drive wiring portion 352 a passes throughthe second outer torsion bar 318 b on the lower side, extends to theleft on the support 320, and terminates at an electrode pad 366 aprovided on the support 320.

As is obvious from FIG. 11, the first outer extracted wiring portion 354a and first outer extracted wiring portion 356 a are located almostline-symmetrically with respect to the first axis A1.

The second outer extracted wiring portion 354 b extending from the upperend portion of the second outer drive wiring portion 352 b on the rightside passes through the first outer torsion bar 318 a on the upper side,extends to the right on the support 320, and terminates at an electrodepad 364 b provided on the support 320.

The second outer extracted wiring portion 356 b extending from the lowerend portion of the second outer drive wiring portion 352 b passesthrough the second outer torsion bar 318 b on the lower side, extends tothe right on the support 320, and terminates at an electrode pad 366 bprovided on the support 320.

As is obvious from FIG. 11, the second outer extracted wiring portion354 b and second outer extracted wiring portion 356 b are located almostline-symmetrically with respect to the first axis A1.

Although not specifically shown, the wirings 330 a, 330 b, 350 a, and350 b are covered with isolation film such as silicon oxide film forelectric isolation.

As shown in FIG. 12, the magnet unit 380 includes a magnet 382 locatedat the center and a magnet 384 surrounding the magnet 382. The magnet382 has an N pole on the side facing the movable plate units 310, andthe magnet 384 has an S pole on the side facing the movable plate units310. That is, the magnets 382 and 384 are opposite in magnetic polaritydirection. The magnet 382 has an elliptic cylindrical shape. The magnet384 has a through hole in which the magnet 382 is fitted. The magnet 382is placed in this though hole. Therefore, the outer peripheral shape ofthe magnet 382 is elliptic when viewed from the above.

Parts of the boundary between the magnets 382 and 384 that extend alongthe minor axis of the elliptic shape of the magnet 382 are locatedalmost immediately below the inner drive wiring portions 332 a and 332b, respectively. In addition, parts of the boundary between the magnets382 and 384 that extend along the major axis of the elliptic shape ofthe magnet 382 are located almost immediately below the outer drivewiring portions 352 a and 352 b, respectively.

The magnetic flux density near the boundary between the magnets 382 and384, which are opposite in magnetic polarity direction, is high. Forthis reason, both portions near the middles of the inner drive wiringportions 332 a and 332 b (portions relatively near the second axis A2)and portions near the middles of the outer drive wiring portions 352 aand 352 b (portions relatively near the first axis A1) are located inregions where the magnetic flux densities are high.

As shown in FIG. 10, the magnetic lines of force flowing from the magnet382 to the magnet 384 cross the portions near the middles of the innerdrive wiring portions 332 a and 332 b and the portions near the middlesof the outer drive wiring portions 352 a and 352 b at almost rightangles.

In this embodiment, the inner movable plate 312 is actuated about thefirst axis A1 in the same manner as in the first embodiment except thatthe magnitudes of Lorentz forces received by the inner drive wiringportions 332 a and 332 b when currents flow in the inner wirings 330 aand 330 b depend on positions. The Lorentz force forces received by theinner drive wiring portions 332 a and 332 b are highest near the middlesof the wiring portions, and the Lorentz forces received by parts of theinner drive wiring portions 332 a and 332 b that are near their middlescontribute most to the actuation of the inner movable plate 312.

In addition, the outer movable plate 316 is actuated about the secondaxis A2 in the same manner as in the first embodiment except that themagnitudes of Lorentz forces received by the outer drive wiring portions352 a and 352 b when currents flow in the outer wirings 350 a and 350 bdepend on positions. The Lorentz force forces received by the outerdrive wiring portions 352 a and 352 b are highest near the middles ofthe wiring portions, and the Lorentz forces received by parts of theouter drive wiring portions 352 a and 352 b that are near their middlescontribute most to the actuation of the outer movable plate 316.

In the two-dimensional optical deflector 300 of this embodiment, sincethe inner movable plate 312 is in the form of a circular plate, itsinertia moment is smaller than that of a movable plate in the form of arectangular plate (i.e., the inner movable plate 112 in the firstembodiment). In addition, since the outer movable plate 316 is in theform of a circular frame, its inertia moment is smaller than that of amovable plate in the form of a rectangular frame (i.e., the outermovable plate 116 in the first embodiment). This allows the springstiffness of the inner torsion bars 314 a and 314 b and outer torsionbars 318 a and 318 b to be reduced with the resonant frequencymaintained, so that actuating operation with small currents, i.e., areduction in power consumption is realized.

In this embodiment, each of the inner wirings 330 a and 330 b makes ahalf turn on the inner movable plate 312. However, each wiring may makemore turns. Likewise, each of the outer wirings 350 a and 350 b makes ahalf turn on the outer movable plate 316. However, each wiring may makemore turns.

Although the embodiments of the present invention have been describedwith reference to the views of the accompanying drawing, the presentinvention is not limited to these embodiments, and various modificationsand changes thereof can be made within the spirit and scope of theinvention.

Each embodiment described above is directed to a two-dimensional unitoptical deflector. However, such deflectors may be properly arrangedinto an array.

In the first embodiment, the magnet unit includes five magnets. In thethird embodiment, the magnet unit includes three magnets. However, thenumber of magnets constituting the magnet unit is not limited to them aslong as the boundary between two magnets that are opposite in magneticpolarity direction and adjacent to each other is placed almost parallelalmost immediately below the drive wiring portion.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. An electromagnetically actuated optical deflector comprising: amagnet unit, which generates a magnetic field; and a movable plate unit,which is placed in the magnetic field, the movable plate unit having aninner movable plate having a reflecting surface, an outer movable platelocated outside the inner movable plate, two inner torsion barsconnecting the inner movable plate and the outer movable plate, asupport located outside the outer movable plate, and two outer torsionbars connecting the outer movable plate and the support, the innertorsion bars extending along a first axis and being capable of twistingabout the first axis so as to allow the inner movable plate to tiltabout the first axis with respect to the outer movable plate, the outertorsion bars extending along a second axis perpendicular to the firstaxis and being capable of twisting about the second axis so as to allowthe outer movable plate to tilt about the second axis with respect tothe support, the movable plate unit further having two inner drivewiring portions that extend along by a periphery of the inner movableplate, and the magnet unit including magnets, two adjacent magnets ofthe magnets being opposite in magnetic polarity direction, the innerdrive wiring portions extending substantially parallel to boundariesbetween the two adjacent magnets and being respectively locatedsubstantially immediately above the boundaries, and currents of the samedirection being applied to the two inner drive wiring portions.
 2. Adeflector according to claim 1, wherein an outer peripheral shape of theinner movable plate is a rectangular shape, and two central axes of therectangular shape, which are perpendicular to each other, are parallelto the first and second axes, respectively.
 3. A deflector according toclaim 1, wherein an outer peripheral shape of the inner movable plate isan elliptic shape (including a circular shape), and two central axes ofthe elliptic shape, which are perpendicular to each other, are parallelto the first and second axes, respectively.
 4. A deflector according toclaim 1, wherein the movable plate unit further has two outer drivewiring portions that extend along by a periphery of the outer movableplate, the outer drive wiring portions extending substantially parallelto boundaries between the two adjacent magnets and being respectivelylocated substantially immediately above the boundaries, and currents ofthe same direction being applied to the two outer drive wiring portions.5. A deflector according to claim 4, wherein an outer peripheral shapeof the outer movable plate is a rectangular shape, and two central axesof the rectangular shape, which are perpendicular to each other, areparallel to the first and second axes, respectively.
 6. A deflectoraccording to claim 4, wherein an outer peripheral shape of the outermovable plate is an elliptic shape (including a circular shape), and twocentral axes of the elliptic shape, which are perpendicular to eachother, are parallel to the first and second axes, respectively.
 7. Adeflector according to claim 4, wherein the two inner drive wiringportions are located substantially line-symmetrically with respect tothe first axis and the two outer drive wiring portions are locatedsubstantially line-symmetrically with respect to the second axis.
 8. Adeflector according to claim 7, wherein the magnet unit includes amagnet located at the center, two magnets arranged at two sides of themagnet the along first axis, and two magnets arranged at two sides ofthe magnet along the second axis.
 9. A deflector according to claim 7,wherein the magnet unit includes a magnet located at the center andanother magnet surrounding the magnet.
 10. A deflector according toclaim 9, wherein an outer peripheral shape of the magnet located at thecenter is rectangular.
 11. A deflector according to claim 9, wherein anouter peripheral shape of the magnet located at the center is elliptic.12. An electromagnetically actuated optical deflector comprising: amagnet unit, which generates a magnetic field; and a movable plate unit,which is placed in the magnetic field, the movable plate unit having amovable plate having a reflecting surface, a support located outside themovable plate, and two torsion bars connecting the movable plate and thesupport, the torsion bars extending along one axis and being capable oftwisting about the axis so as to allow the movable plate to tilt aboutthe axis with respect to the support, the movable plate unit furtherhaving two drive wiring portions that extend along by a periphery of themovable plate, and the magnet unit including magnets, two adjacentmagnets of the magnets being opposite in magnetic polarity direction,the drive wiring portions extending substantially parallel to boundariesbetween the two adjacent magnets and being respectively locatedsubstantially immediately above the boundaries, and currents of the samedirection being applied to the two drive wiring portions.
 13. Adeflector according to claim 12, wherein the two drive wiring portionsare substantially line-symmetrically with respect to the axis.
 14. Adeflector according to claim 13, wherein the magnet unit includes amagnet located at the center and two magnets located on two sides of themagnet along a direction perpendicular to the axis.
 15. A deflectoraccording to claim 13, wherein the magnet unit includes a magnet locatedat the center and another magnet surrounding the magnet.
 16. Anelectromagnetically actuated optical deflector comprising: a magnetunit, which generates a magnetic field; and a movable plate unit, whichis placed in the magnetic field, the movable plate unit having a movableplate having a reflecting surface, a first support located outside themovable plate, and two first torsion bars connecting the movable plateand the first support, the first torsion bars extending along a firstaxis and being capable of twisting about the first axis so as to allowthe movable plate to tilt about the first axis with respect to the firstsupport, the movable plate unit further having two first drive wiringportions that extend along by a periphery of the movable plate, the twofirst drive wiring portions being located substantiallyline-symmetrically with respect to the first axis, and the magnet unitincluding magnets, two adjacent magnets of the magnets being opposite inmagnetic polarity direction, the first drive wiring portions extendingsubstantially parallel to boundaries between the two adjacent magnetsand being respectively located substantially immediately above theboundaries, and currents of the same direction being applied to the twofirst drive wiring portions.
 17. A deflector according to claim 16,further comprising a second support located outside the first supportand two second torsion bars connecting the first support and the secondsupport, the second torsion bars extending along a second axissubstantially perpendicular to the first axis and being capable oftwisting about the second axis so as to allow the first support to tiltabout the second axis with respect to the second support, and whereinthe movable plate unit further has two second drive wiring portions thatextend along by the periphery of the first support, the two second drivewiring portions being located substantially line-symmetrically withrespect to the second axis, and the second drive wiring portionsextending substantially parallel to boundaries between the two adjacentmagnets and being respectively located substantially immediately abovethe boundaries, and currents of the same direction being applied to thetwo second drive wiring portions.